This invention relates to novel rosin-fatty acid vinylic polymer compositions that exhibit characteristics which make them useful as grind resins for preparing grind vehicles for ink and coating formulations. In particular, this invention relates to rosin-fatty acid vinylic grind resin compositions produced from the addition polymerization reaction of a mixture of rosin and fatty acid and a mixture of (meth)acrylic and vinylic monomers.
Impelled by environmental concerns and increasing governmental regulations on the volatile organic content of coatings, the applications of water-based inks are increasing in the ink industry. A typical water-based ink system is formulated by the addition of a pigment to a grind resin. These grind vehicles are prepared by using grinding resins to disperse pigments. Typically, such grind resins are cut into aqueous ammonia at a pH of about 8.5 and the resulting solutions are employed to grind the pigments. Pigments are crystalline solids composed of agglomerates, aggregates, and primary particles which vary in size from 0.02 to 0.50 microns. During the grinding process, agglomerates and aggregates are broken down into primary particles which possess strong tendencies to reassociate in an ink. The finer the particle size of the pigment, the greater the color strength, but the more difficult the pigment becomes to disperse. Grinding resins help prevent the particles from reassociating by increasing both the electrostatic and steric repulsion between pigment particles.
The traditional process for producing polymer resins is well known (see generally U.S. Pat. Nos. 4,839,413 and 5,216,064, which are hereby incorporated by reference). Commonly a solution polymerization reaction is employed wherein styrenic monomer and acrylic acid is mixed with a hydrocarbon solvent, a polymerization initiator, and a chain transfer agent. Upon completion of the reaction, the solution is stripped of the solvent to yield the acrylic polymer (which may subsequently be employed as a grind resin).
However, major problems exist with the traditional methods of producing such grind resins. For example, these methods require the use of environmentally adverse hydrocarbon solvents. Moreover, as these solvents are not usable or desirable in water-based ink formulations, the solvents must be stripped from the resulting acrylic polymers (thereby causing a yield loss). This stripping step also adds expense to the process due to both the loss of yield and the energy consumed in performing the stripping. Also, these methods must utilize chain transfer agents to regulate the molecular weight of the resulting grind resins.
Therefore, an object of this invention is to solve these major problems by disclosing rosin-fatty acid vinylic polymer grind resins.
Another object of this invention is to disclose a method of producing rosin-fatty acid vinylic polymer compositions which exhibit properties that make them useful as grind resins for formulating grind vehicles for inks and other coatings.
The objects of this invention are met by via a method that employs rosin and fatty acid to act as solvents in the polymerization reaction of the acrylic monomers, thereby producing rosin-fatty acid vinylic polymer compositions which exhibit properties that make them useful as grind resins in inks and other coating applications. As this method does not require the use of hydrocarbon solvents, the need for solvent stripping is eliminated. Also, the polymerization reaction can be conducted at higher temperatures (i.e., up to boiling point of fatty acid) than traditional solution polymer methods, thereby allowing the practitioner to utilize smaller amounts of free radical initiators. Furthermore, the practitioner is able to regulate molecular weight without the use of chain Bit transfer agents, thereby both reducing costs and avoiding the production of unpleasant odors associated with such agents. Moreover, the fatty acid and rosin can function as a reactive diluent to impart flexibility to the grind resins.
The rosin-fatty acid vinylic polymer grinding resin compositions comprise the addition polymerization reaction products of:
(A) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(1) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of fatty acid, and
(2) about 10.0% to about 90.0% by total weight of the fatty acid rosin mixture of rosin; and
(B) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(1) about 15.0% to about 45.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, and combinations thereof,
(2) about 55.0% to about 85.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(3) about 0.5% to about 5.0% by total weight of the monomer mixture of a polymerization initiator,
(4) up to about 4.0% by total weight of the monomer mixture of a chain transfer agent, and
(5) up to about 30.0% by total weight of the monomer mixture of a hydrocarbon solvent; at a temperature in the range of about 135xc2x0 C. to about 175xc2x0 C. to produce the rosin-fatty acid vinylic polymer grinding resin compositions having a weight average molecular weight in the range of about 4,000 to about 12,000.
Preferred rosin-fatty acid vinylic polymer grinding resin compositions comprise the addition polymerization reaction products of:
(A) about 20.0% to about 60.0% by total weight of the reactants of a fatty acid rosin mixture comprising:
(1) about 20.0% to about 50.0% by total weight of the fatty acid rosin mixture of fatty acid, and
(2) about 50.0% to about 80.0% by total weight of the fatty acid rosin mixture of rosin; and
(B) about 40.0% to about 80.0% by total weight of the reactants of a monomer mixture comprising:
(1) about 20.0% to about 25.0% by total weight of the monomer mixture of a member selected from the group consisting of acrylic acid, methacrylic acid, and combinations thereof,
(2) about 60.0% to about 70.0% by total weight of the monomer mixture of a member selected from the group consisting of vinylic monomers and combinations thereof,
(3) about 1.0% to about 3.0% by total weight of the monomer mixture of a polymerization initiator,
(4) about 0.5% to about 2.0% by total weight of the monomer mixture of a chain transfer agent, and
(5) about 1.0% to about 4.0% by total weight of the monomer mixture of a hydrocarbon solvent;
at a temperature in the range of about 135xc2x0 C. to about 175xc2x0 C. to produce the rosin-fatty acid vinylic polymer grinding resin compositions having a weight average molecular weight in the range of about 4,000 to about 12,000.
The addition polymerization reaction used to produce the rosin-fatty acid vinylic polymer grinding resin compositions is a melt polymerization reaction in which no water is employed. Reaction temperatures suitable for use in the present method are within the range of about 135xc2x0 C. to about 175xc2x0 C.; with the preferred temperatures being in the range of about 140xc2x0 C. to about 170xc2x0 C.
The rosin and fatty acid function as solvents in the polymerization reaction of the acrylic monomers. Additionally, while a portion of the fatty acid and the rosin component remains unreacted, some of the fatty acid and rosin becomes graft polymerized onto the acrylic. The resulting rosin-fatty acid vinylic polymer grinding resin compositions have a weight average molecular weight in the range of about 4,000 to about 12,000; with the preferred molecular weights being in the range of about 5,000 to about 11,000.
These rosin-fatty acid vinylic polymer compositions have characteristics which differ from the traditional melt blends of flake acrylic fatty acid rosin. For example, the low molecular weights of the rosin-fatty acid vinylic polymers enable the polymers to be neutralized at high solid levels while maintaining low viscosities. The low molecular weight coupled with the polymer""s high levels of functional carboxyl units permits the production of grinding resins which contain high amounts of functional polymers components while maintaining targeted viscosity levels for ink formulation purposes.
The rosin-fatty acid vinylic polymer grind resins are well-suited for use in formulating both water-based inks and solvent-based inks, as the grind resins tend to improve both the gloss and the leveling properties of the formulated inks. Grind vehicle for ink formulations can be produced by dispersing the grind resin and the desired ink pigment in solution. Water-based grind vehicles can be produced by dispersing the grind resin and pigment in water via the use of a suitable neutralizing agent; while solvent-based grind vehicles can be produced by dispersing the grind resin and pigment in a suitable solvent.
Fatty acids which are suitable for use in the present method include those fatty acids which contain a range of carbon atoms from about C12 to about C24; with the preferred range being from about C16 to C20. It is further preferred that the fatty acid be vegetable or tall oil based. It is most preferred that the fatty acid be tall oil based and contain from about 15% to about 18% conjugated double bonds.
It is preferred to add from about 20% to about 50% by total weight of the fatty acid rosin mixture of fatty acid.
Rosins which are suitable for use in the present method include wood rosin, tall oil rosin, gum rosin, and the like. The use of tall oil rosin is preferred. It is further preferred to add from about 50% to about 80% by total weight of the fatty acid rosin mixture of rosin.
It is preferred to add from about 20% to about 25% by total weight of the monomer mixture of acrylic acid, methacrylic acid, and combinations thereof.
It is preferred to add from about 60% to about 70% by total weight of the monomer mixture of vinylic monomers. Suitable vinylic monomers include styrenic monomers, acrylic monomers, methacrylic monomers, and the like. It is preferred that the vinylic monomers be a mixture, preferably including at least one monoalkenyl aromatic monomer and at least one acrylic monomer. The monoalkenyl aromatic monomer to be employed includes, for example, alpha-methyl styrene, styrene, vinyl toluene, tertiary butyl styrene, ortho-chlorostyrene and mixtures thereof.
The term xe2x80x9cacrylic monomerxe2x80x9d as employed herein includes acrylic or methacrylic acid, esters of acrylic or methacrylic acid and derivatives and mixtures thereof. Examples of suitable acrylic monomers include the following methacrylate esters: methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, isoamyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, 2-sulfoethyl methacrylate, trifluoroethyl methacrylate, glycidyl methacrylate, benzyl methacrylate, allyl methacrylate, 2-n-butoxyethyl methacrylate, 2-chloroethyl methacrylate, sec-butyl-methacrylate, tert-butyl methacrylate, 2-ethybutyl methacrylate, cinnamyl methacrylate, crotyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, 2-ethoxyethyl methacrylate, furfuryl methacrylate, hexafluoroisopropyl methacrylate, methallyl methacrylate, 3-methoxybutyl methacrylate, 2-methoxybutyl methacrylate, 2-nitro-2-methylpropyl methacrylate, n-octylmethacrylate, 2-ethylhexyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenylethyl methacrylate, phenyl methacrylate, propargyl methacrylate, tetrahydrofurfuryl methacrylate and tetrahydropyranyl methacrylate.
Other suitable acrylic monomers include methacrylic acid derivatives such as methacrylic acid and its salts, methacrylonitrile, methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, N,N-diethymethacrylamide, N,N-dimethylmethacrylamide, N-phenyl-methacrylamide, methacrolein, and the like.
Typical acrylate esters employed include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexal acrylate, n-decyl acrylate, and the like.
Acrylic acid derivatives employed as the acrylic monomer include acrylic acid and its salts, acrylonitrile, acrylamide, methyl alpha-chloroacrylate, methyl 2-cyanoacrylate, N-ethylacrylamide, N,N-diethylacrylamide, acrolein, and the like.
The present invention method is also applied to the preparation of copolymers from mixtures of two or more acrylic monomers such as termonomers and tetramonomers. It is also contemplated that mixtures of at least one acrylic monomer and at least one non-acrylic ethylenic monomer may be polymerized with monoalkenyl aromatic monomers in accordance with the present method.
Suitable ethylenic monomers include vinyl pyridine, vinyl pyrollidone, sodium crotonate, methyl crotonate, crotonic acid, maleic anhydride, and the like.
The type of polymerization initiator suitable for use in the present method is known in the art to depend upon the desired temperature for the reaction. Suitable initiators include, but are not limited to, the following: t-butyl peroxide, t-butyl peroxybenzoate, t-butyl peroctoate, cumene hydroperoxide, azobisisobutyronitrile, benzoyl peroxide, and combinations thereof. It is preferred to add from about 1.0% to about 3.0% by total weight of the monomer mixture of polymerization initiator.
Where desired, a chain transfer agent may be employed in the present method. Chain transfer agents which are suitable for use in the above reaction include, but are not limited to, the following: dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid, octyl mercaptan, 2-mercaptoethanol, and combinations thereof. Where employed, it is preferred to use an amount of chain transfer agent in the range of from about 0.5% to about 2.0% by total weight of the monomer mixture of chain transfer agent.
Where desired, a hydrocarbon solvent may be employed in the present method. Suitable hydrocarbon solvents include aromatic solvents, aliphatic solvents, and combinations thereof. Where employed, it is preferred to use an amount of hydrocarbon solvent in the range of about 1.0% to about 4.0% by total weight of the monomer mixture.
Rosin-fatty acid vinylic polymer compositions which are suitable for use as grind resins for ink and overprint applications have an acid number in the range of about 175 to about 500; with the preferred range being about 190 to about 230.
It is preferred to employ a bulk polymerization process for the addition polymerization reaction. The residence time for such bulk processes is commonly in the range of about 3 hours to about 10 hours. However, where desired the addition polymerization reaction may be conducted via the use of a continuous stirred polymerization process. The residence time for such continuous processes is commonly in the range of about 90 minutes to about 6 hours; with the preferred residence time being in the range of about 2 hours to about 3 hours.
As appreciated in the art, the exact components and properties of components desired for any coating application can vary and, therefore, routine experimentation may be required to determine the optional components and proportions of components for a given application and desired properties.